IL13 and infection: In the chicken, as in biomedical model species, Th1 cytokine response with interferon-gamma (IFNγ) release predominates in response to infection with intracellular pathogens like viruses, while Th2 cytokines such as interleukin 10 and 13 (IL10, IL13) are released in responses to infection with extracellular pathogens like bacteria.